Penelitian ini bertujuan untuk menghasilkan model pembelajaran Penalaran Penyelesaian Masalah (P2M) yang layak (valid, praktis, dan efektif) untuk meningkatkan penalaran proporsional dan kemampuan penyelesaian masalah fisika. Penelitian ini merupakan penelitian pengembangan dengan tahapan studi pendahuluan, perancangan model hipotetik, operasionalisasi model, dan implementasi dengan mengikuti rancangan Wademan dan Mckenney. Subjek implementasi dalam penelitian ini adalah siswa kelas XI SMA Negeri 1 Galesong Utara yang berjumlah 240 siswa yang dipilih secara purposive sampling. Data penelitian berupa validitas dikumpulkan melalui instrumen lembar validasi model pembelajaran, data kepraktisan dikumpulkan melalui instrumen lembar pengamatan keterlaksanaan pembelajaran dan lembar pengamatan aktivitas siswa, dan data keefektifan dikumpulkan melalui instrumen penalaran proporsional, instrumen kemampuan penyelesaian masalah, dan angket respon siswa. Data penelitian dianalisis secara deskriptif kuantitatif yaitu nilai rata-rata dan persentase, dan juga statistik inferensial dengan menggunakan uji-t dan uji ANOVA.  Berdasarkan hasil analisis data penelitian diperoleh bahwa model pembelajaran P2M telah memenuhi kategori valid secara konten dan konstruk; praktis ditinjau dari keterlaksanaan RPP yang berada pada kategori terlaksana baik dan sangat baik, dan aktivitas belajar siswa berkategori baik; serta efektif ditinjau dari respon positif siswa sangat kuat, ada peningkatan keterampilan penalaran proporsional, dan kemampuan penyelesaian masalah fisika siswa pada a = 5%, rata-rata n-gain berkategori sedang dan konsisten. Berdasarkan hasil analisis data, dapat disimpulkan bahwa model pembelajaran Penalaran Penyelesaian Masalah layak untuk meningkatkan penalaran proporsional dan kemampuan penyelesaian masalah fisika.

This research aims to produce a problem solving reasoning (PSR) learning model that is feasible (valid, practical, and effective) to improve the students’ proportional reasoning and problem solving skills in physics learning. This research is a developmental research using the stages of Wademan and Mckenney design: preliminary study, hypothetical model design, model operationalization, and implementation. The subjects of implementation in this research were class XI students of SMA Negeri 1 Galesong Utara, consisting of 240 students selected by purposive sampling. The research data were in the form of data on validity which was collected through learning model validity sheets, data on practicality which was collected by using observation sheet, and data on effectiveness which was gained through proportional reasoning instrument, problem solving instrument, and students’ response questionnaire. The data were analyzed descriptively employing the average and percentage values, and also inferential statistics using t-test and ANOVA test. Based on the results of data analysis, it was found that the P2M learning model was valid, practical, and effective. The model was claimed valid both in content and construct valitidy; the practicality was shown by the lesson plans implementations which were categorized as good and very good, as well as the students’ learning activities which were also categorized as good; while the effectiveness can be seen from the highly positive response from students, and the students’ improvement in proportional reasoning and problem solving skills at a= 5%, where the average n-gain was categorized as moderate and consistent. Based on the results of data analysis, it can be concluded that the Problem Solving Reasoning learning model is feasible to improve students’ Physics proportional reasoning and problem solving skills.